Various types of exercise devices such as stationary bikes, treadmills, stair climbers, ellipticals, rowing machines, arm bike ergometers, and the like have been developed. Such exercise devices mimic a corresponding physical activity to some degree. For example, known stair climbing machines typically include movable foot supports that reciprocate to simulate to some degree the foot and leg motion encountered when climbing stairs. Known stationary bikes typically include a crank with pedals that rotate upon application of a force to the pedals by a user. Known exercise devices may incorporate flywheels to sustain momentum. Exercise devices may include a resistance mechanism, such as a friction brake, eddy current brake, fluid brake, wind brake, or other brakes that resist rotation of the flywheel to create resistance for the user beyond that which is provided by the rotating mass of the flywheel, friction in the drivetrain, and air resistance of the rotating parts. For example, some exercise devices use a pressure sensitive friction brake mechanism that applies a force to the perimeter of the flywheel according to a user-controlled actuator to provide resistance.
Users may want to know information concerning their level of exertion either for athletic performance or health purposes. Measuring and recording power as an indicator of physical exertion is known. However, this may involve expensive and complicated components that may require frequent adjustment. Existing power measurement systems may also provide insufficient accuracy.
Stationary bikes having power measuring systems have been developed. For example, Ambrosina et al., U.S. Pat. No. 6,418,797, discloses a torque measurement system incorporated into the hub of a bike to determine torque applied by the user, and the torque is then used to calculate power. A commercial system related to the system disclosed in the Ambrosina '797 patent is available from Saris Cycling Group, Inc. of Madison, Wis.
Another aspect of the present invention includes utilizing the power data to measure and record the force or power the user applies throughout 360 degrees of the pedal stroke with each leg or both legs, 360 degrees of the elliptical stroke with each leg or both legs, 360 degrees of the handle stroke with each arm or both arms, or throughout the range of another movement regardless of the shape or path of that movement with whatever limb or limbs are used to apply force during that exercise. This may be useful in teaching users how to apply force smoothly, and/or efficiently.
Also, a system according to the present invention may be utilized to determine right leg and left leg symmetry in terms of force and/or power production, which can be measured, displayed, and recorded.
Various ways to control the forces generated by such exercise devices have been developed. Known control schemes include constant-force arrangements and constant-power arrangements. Also, some exercise devices vary the force required in an effort to simulate hills or the like encountered by a user.